This invention relates to liquid crystal display devices and particularly to the structure of a liquid crystal display cell integrated with circuit elements for operating the liquid crystal display cell.
A typical liquid crystal display device consists of a liquid crystal display cell and driving and logic circuitry associated therewith. The display cell comprises a thin layer of a liquid crystal composition between two parallel electrodes, at least one of which is segmented. In any area of the liquid crystal composition to which a low voltage activating signal is applied, the optical properties of the composition are altered, thereby modulating light passing therethrough or impinging thereon. Generally, light modulation occurs due to a change in either the light scattering properties of the liquid crystal material or the rotation of the plane of polarization of light passing therethrough upon the application of the activating voltage thereto. Typically, thin layers of a liquid crystal composition which modulates light due to a change in its light scattering properties changes in appearance from transparent to white upon the application of an activating voltage. However, materials are known which appear white in the absence of an applied voltage and become clear upon the application of an activating voltage. Liquid crystal devices which operate based upon a change in the direction of polarization upon the application of a field are also known. In these devices the display cell is placed between polarizers when operating with white light. These latter devices may change in appearance from dark to white or vice versa upon the application of an activating voltage.
In addition, liquid crystal devices can be operated in either a reflective or transparent mode. Liquid crystal display devices require very little power for operation and maintain excellent brightness and contrast under high ambient light conditions.
The present invention provides a liquid crystal display device which permits the fabrication of miniaturized, compact devices at relatively low costs. The device may operate in any of the aforementioned modes or contain any known electro-optically responsive liquid crystal composition or other electro-optic responsive material, such as particles suspended in a liquid vehicle.
For many applications of liquid crystal display devices such as wrist watches and portable calculators, compactness of the device is essential for commercial success and every improvement toward miniaturization of the device is of importance.
Characteristically, the circuit elements which comprise the logic, control, drive and switching circuits for operating the liquid crystal display cell of the display device are remote from the display cell or at least are mounted upon a common substrate together with a prefabricated display cell. This latter approach, while greatly preferred over remotely situated circuit elements, when compactness is required, add to the thickness of the overall device by requiring a substrate which is in addition to and independent from display cell and upon which the display cell is mounted.
The present invention provides a structure which can further miniaturize the liquid crystal display device at least by reducing the thickness of the device. The structure of the present invention also reduces or eliminates the need for bonding separate thin wire leads from the display cell segments to the appropriate circuit elements. This results in a cost reduction of the fabricated device.